Re: [aspectj-dev] weaving information via messages

[Wes Isberg <wes@xxxxxxxxxxxxxx>]

Hi Martin -

This would be interesting information, and a good feature request to put in the
bug database.  There's a lot of similar information that clients might like. 
Before we go down the road of adding message types and instrumenting the
compiler in various (scattered?) places, we should consider whether that's where
this feature belongs.  

Normally, we try to use AJDE for API clients of compiler to insulate the
compiler code from extraneous concerns, so perhaps your feature request should
be addressed to AJDE. Normally we think of ADJE as supporting IDE's, but perhaps
it should also be used for non-IDE clients of static structure.  

One question is whether AJDE could work well here with the process of load-time
weaving. If load-time weaving is one long compile process, handling each new set
of bytecode in turn, it never "completes", per se:

- all aspects loaded
- load class
  - get bytecode
  - weave bytecode
    - load any required classes
      - for already-defined classes, get from classloader
      - for undefined classes, do {nested} load/weave 
  - define class
...

I'm not sure if AJDE is set up to provide in-process signals or surface a
partial structure model before a compile has completed.  If it is, we should use
that.  If not, we should consider whether that's where we should be putting
these efforts.

There are other alternatives.  The bytecode weaver could annotate the woven
class with attributes listing aspects which affect it, which could be pulled
when weaving was completed from the live model and could be available for other
static analysis tools aware of the attribute (We could surface an API for a
decompiler which would understand any custom attributes we put in the .class
files.)  That in effect creates a data interface rather than an API interface.

If we do put this in the compiler and the signals are scattered, then this is a
good candidate for an aspect to provide the in-process messages, after we commit
to building AspectJ with AspectJ.

Finally, I should say that before we add features to support load-time weaving,
I'd like to have a weaving class loader implemented with tests and available in
the download for people to use.  I appreciate your contribution[1], but we
haven't quite finished this process for (and in light of) 1.1.

Thanks for bringing this up.
Wes

[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=31460

Martin Lippert wrote:
> 
> Hi,
> 
> for the dynamic weaving functionality that I implemented for the Eclipse
> runtime I need to know which aspect got woven into which class.
> Therefore it would be good if the weaver would generate messages during
> the bytecode weaving. Those specialized messages could contain
> information for the aspect and the class.
> I implemented a special subclass of Message and added the creation of
> the message to the BcelAdvice class (a simple test case for this as
> well). I used the Message.INFO kind for this to not modify the IMessage
> interface. It might be better to have a special IMessage.Kind for that,
> something like "WOVEN". What do you think about this kind of information
> mechanism?
> 
> In addition to that I believe there are more places (in addition to
> BcelAdvice.implementOn(..)) where this kind of information should be
> generated, but I do not know exactly, where they are. Do you have any
> idea where I should put this message creation, too?
> 
> Best regards,
> Martin
> 
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